Identification of the primary cell type in which the Epstein-Barr virus (EBV) replicates is essential to understanding the biology of the virus, mode of transmission and pathogenesis. Virtually all we know about EBV comes froms studies of the virus in relation to lymphoid tissue. Yet, EBV is linked to three quite different diseases with involvement of not only lymphoid but also epithelial elements. The goal of this study is to define the effects of cell differentiation on EBV-epithelial cell interaction. Differences in membrane receptor expression, EBV-specific antigen expression, transcriptional patterns of the EBV genome, and virus productivity will be examined in both undifferentiated and differentiated epithelial cell subsets. These determinations will be made by indirect immunofluorescence techniques; electron microscopy; DNA-RNA cytohybridization with a new generation of cloned, biotinylated DNA probes; and by standard lymphocyte transformation assays. Studies of host cell control of infection are only now possible in this epithelial cell system with the establishment of techniques for long-term maintenance of primary explant cultures in an undifferentiated state and synchronized induction of cell differentiation. The problems imposed on EBV pathogenesis by the apparent lack of host cell receptors will also be addressed by infection and cocultivation of autologous lymphoid and epithelial cell populations. Evidence for transforming potential of EBV in epithelial cells will be sought in long-term cell cultures infected with wild-type EBV strains or transfected with either cloned EBV DNA fragments or cellular DNA from autologous lymphoblastoid cell cultures. Ease of cell passage, ability to grow in soft agar, and oncogenicity in nude mice will be assessed. Clinical correlates will be sought by cytohybridization analyses of benign lymphoepithelial lesions of the parotid and salivary glands as well as by delineation of selectively encoded regions of the EBV genome in oropharyngeal epithelial cells from various patient groups.